netdev - Re: [PATCH bpf] bpf: Fix IPv6 dport byte order in bpf_sk_lookup

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Date:   Wed, 7 Nov 2018 21:55:23 +0000
From:   Martin Lau <kafai@...com>
To:     Andrey Ignatov <rdna@...com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "joe@...d.net.nz" <joe@...d.net.nz>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH bpf] bpf: Fix IPv6 dport byte order in bpf_sk_lookup_udp

On Wed, Nov 07, 2018 at 01:36:07PM -0800, Andrey Ignatov wrote:
> Lookup functions in sk_lookup have different expectations about byte
> order of provided arguments.
> 
> Specifically __inet_lookup, __udp4_lib_lookup and __udp6_lib_lookup
> expect dport to be in network byte order and do ntohs(dport) internally.
> 
> At the same time __inet6_lookup expects dport to be in host byte order
> and correspondingly name the argument hnum.
> 
> sk_lookup works correctly with __inet_lookup, __udp4_lib_lookup and
> __inet6_lookup with regard to dport. But in __udp6_lib_lookup case it
> uses host instead of expected network byte order. It makes result
> returned by bpf_sk_lookup_udp for IPv6 incorrect.
> 
> The patch fixes byte order of dport passed to __udp6_lib_lookup.
> 
> Originally sk_lookup properly handled UDPv6, but not TCPv6. 5ef0ae84f02a
> fixes TCPv6 but breaks UDPv6.
> 
> Fixes: 5ef0ae84f02a ("bpf: Fix IPv6 dport byte-order in bpf_sk_lookup")
> Signed-off-by: Andrey Ignatov <rdna@...com>
Good catch.

Acked-by: Martin KaFai Lau <kafai@...com>

> ---
>  net/core/filter.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index e521c5ebc7d1..9a1327eb25fa 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -4852,18 +4852,17 @@ static struct sock *sk_lookup(struct net *net, struct bpf_sock_tuple *tuple,
>  	} else {
>  		struct in6_addr *src6 = (struct in6_addr *)&tuple->ipv6.saddr;
>  		struct in6_addr *dst6 = (struct in6_addr *)&tuple->ipv6.daddr;
> -		u16 hnum = ntohs(tuple->ipv6.dport);
>  		int sdif = inet6_sdif(skb);
>  
>  		if (proto == IPPROTO_TCP)
>  			sk = __inet6_lookup(net, &tcp_hashinfo, skb, 0,
>  					    src6, tuple->ipv6.sport,
> -					    dst6, hnum,
> +					    dst6, ntohs(tuple->ipv6.dport),
>  					    dif, sdif, &refcounted);
>  		else if (likely(ipv6_bpf_stub))
>  			sk = ipv6_bpf_stub->udp6_lib_lookup(net,
>  							    src6, tuple->ipv6.sport,
> -							    dst6, hnum,
> +							    dst6, tuple->ipv6.dport,
>  							    dif, sdif,
>  							    &udp_table, skb);
>  #endif
> -- 
> 2.17.1
>